The present invention relates to methods of making micro-miniature switch devices, and more particularly, to making micro-miniature switch devices utilizing semiconductor fabrication techniques.
High-speed micro-miniature switch devices are used in various technologies, including, for example, vehicle safety systems and microwave relay systems. The number of applications for such switch devices is ever increasing. Thus, there exists an ever-increasing demand for such switch devices.
One example type of vehicle safety systems that often employ micro-miniature switch devices is occupant protection systems that include an air bag module, a seat belt pretensioner, or the like. Typically in such an occupant protection system, an electronic acceleration sensor provides an electrical signal that is proportional to sensed vehicle acceleration. A microprocessor assesses changes in the vehicle acceleration to determine whether the signal indicates that a vehicle crash event that requires actuation of the occupant protection device is in progress.
A safing switch is often used in combination with the acceleration sensor to provide a redundant level of detection for a vehicle crash event. The safing switch usually is designed and calibrated to close at a relatively early stage in a crash event. The occupant protection device is only actuated when the safing switch is closed and the microprocessor determines that the severity of the crash is sufficient to warrant such actuation. There is a current trend to use micro-miniature switches as the safing switches in the vehicle safing switches.
Processes generally similar to those to assemble other small mechanical devices may be used to manufacture micro-miniature switches. However, it is believed that large-scale manufacture of micro-miniature switches using such techniques would not be efficient.
Some efforts are being made to manufacture micro-miniature switches using techniques similar to those used to manufacture semiconductor components and/or micro-machined silicon elements. However, present manufacturing processes often require a relatively large number of process steps. The process steps may include the use of separate and distinct photolithography masks. Also, plural steps often require exact alignment between different masks so that a slight tolerance in each subsequent processing step does not result in errors that prevent the production of functional switches. In addition, each additional processing step generally adds to the cost of the final product.
In accordance with a first aspect, the present invention provides a method of making a micro-miniature switch device that has at least one member movable relative to a substrate upon which the device is provided. A layer of sacrificial non-photolithography material is provided upon a stratum connected to the substrate. A photolithographing step using a photoresist material upon a stratum connected to the substrate provides a template. A layer is provided to comprise at least a portion of the movable member. The photoresist material and the sacrificial non-photolithography material are removed using photoresist developer.
In accordance with a further aspect, at least two photolithography process steps of the method utilize a single photolithographic mask. In accordance with a yet another aspect, substrate material is removed to create a recess and at least one channel into the substrate, wherein the channel intersects the recess. At least a portion of the movable member is provided at a location within the recess and at least a portion of the movable member is provided at a location within the channel.